This invention relates to a method and apparatus for measuring friction torque associated with a motor under test.
Friction torque can result from friction generated in a test fixture by the bearings which support various components of that fixture. For example, when testing electric motors, the motor will be brought into position and coupled to an inertial flywheel which has coupled to it an incremental encoder, as described in U.S. Pat. No. 5,218,860. Friction can also result from misalignment of the motor shaft with respect to the test fixture shaft, thus causing side loading. Another source 15 of friction torque is the result of tight motor bearings; in many cases, the motor bearings will free up after the motor runs for some period of time, however, to obtain an accurate measure of the torque output of a motor, it would be desirable to compensate the measured torque for this initial bearing tightness.
Measuring friction torque would thus allow an accurate determination off the actual torque that can be generated by an electric motor, thus providing a more accurate indication of the quality of the motor itself.